At present, there exists a trend for spacefaring countries to use methane as fuel for the first stages of launch vehicles. Russia is currently developing a promising launch vehicle known as Amur LNG. However, due to methane being a hazardous (flammable and explosive) substance, it is poorly suited for fuel tank strength tests conducted using existing equipment. In this regard, we face an urgent issue of developing a safe method for simulating liquid methane temperature during strength testing of methane tanks. We propose to cool the tank with a nitrogen vapour-liquid mixture. To estimate cooling time for a cryogenic tank treated with a nitrogen vapour-liquid mixture as per the method proposed, along with determining the amount of refrigerant to be used, we solved its thermal state problem using the method of isothermal nodes. This approach may also be used for oxygen tanks.

Russian enterprises continue developing rocket and space vehicles based on cryogenic propellants, i.e. liquid hydrogen, oxygen, and methane. Hence, the issues of fuel tanks’ thermal strength are increasingly important. During structural tests, the operating temperatures of the test object should be simulated, since the temperature condition affects the strength and rigidity of the structure. Consequently, during ground-based experimental tests, hydrogen tanks must be cooled down to 20 K, the boiling point of hydrogen. JSC TsNIIMash is developing a helium system capable of cooling large-sized structures to a temperature of 20 K. Helium can be used in a gaseous state to cool down the structure, since the boiling point of helium, 4 K, is lower than the boiling point of hydrogen. Until now, the tanks were cooled only by filling with liquid nitrogen, therefore the temperature state of the tanks during the tests was simulated only for this case. In order to determine the applicability of the method developed, the cooling time of large-sized containers was estimated by cooling a hydrogen tank, which by its dimensions is typical for an advanced medium-class second stage launcher, to 20 K by gaseous helium.